Is the prospect of group marriage far-fetched? Probably not. There are several avenues that could soon lead to legal recognition of unions involving three or more people. The efforts come from the fringes of the left, from the darkest corners of the fundamentalist right, and from the laboratories of fertility clinics and hard scientists around the world.

From the fringy left: Polyamory

Polyamory describes relationships of three or more people -- it literally means "many loves." Polyamorists say they practice "ethical non-monogamy," or relationships that emphasize open communication, respect, and fair treatment of one another.

The debate about legal recognition of polyamorous relationships is already well underway. A major report issued in 2001 by the Law Commission of Canada asked whether marriages should be "limited to two people." Its conclusion: probably not. A British law professor wrote in an Oxford-published textbook that the idea that marriage meaning two people is a "traditional" and perhaps outdated way of thinking. Elizabeth Emens of the University of Chicago Law School published a substantial legal defense of polyamory in a legal journal. She suggested that "we view this historical moment, when same-sex couples begin to enter the institution of marriage, as a unique opportunity to question the mandate of compulsory monogamy."

Mainstream cultural leaders have also hinted at or actively campaigned for polyamory. Roger Rubin, former vice-president of the National Council on Family Relations--one of the main organizations for family therapists and scholars in the United States--believes the debate about same-sex marriage has "set the stage for broader discussion over which relationships should be legally recognized." The Alternatives to Marriage Project, whose leaders are featured by national news organizations in stories on cohabitation and same-sex marriage, includes polyamory among its important "hot topics" for advocacy. The Unitarian Universalists for Polyamorous Awareness hope to make their faith tradition the first to recognize and bless polyamorous relationships. Meanwhile, a July 2009 Newsweek story estimates that there are more than half a million "open polyamorous families" living in America. Nearly every major city in the U.S. has a polyamory social group of some kind.

If polyamorists are too busy juggling multiple intimate relationships to have time to push for marriage rights, their supporters might fight the battle for them. In an influential document, "Beyond Same-Sex Marriage: A New Strategic Vision for All Our Families and Relationships," released in 2006, over three hundred gay and lesbian activists and their supporters--including attorneys, academics, grassroots leaders, and luminaries such as Gloria Steinem, Barbara Ehrenreich, and well-known professors from the Ivy Leagues--called for "legal recognition for a wide range of relationships, households and families" including "households in which there is more than one conjugal partner."

From the radical right: Polygamy

Coming from a very different direction, another challenge to the two-person understanding of marriage is resurging--polygamy, a marriage form with deep roots in human history and still in evidence in many parts of the world.

The debut in spring 2006 of HBO's television series, Big Love, which featured a fictional and in some ways likeable polygamous family in Utah, propelled polygamy to the front pages of American newspapers and put the idea of legalized polygamy "in play" in some surprising quarters. That March, a Newsweek article with the title "Polygamists Unite!" quoted an activist saying, "Polygamy is the next civil rights battle." "If Heather can have two mommies," he argued, "she should also be able to have two mommies and a daddy." That month the New York Times devoted much attention to the subject of polygamy. One economist snickered that polygamy is illegal mainly because it threatens male lawmakers who fear they would not get wives in such a system. In an opinion piece, then-columnist John Tierney argued that "polygamy isn't necessarily worse than the current American alternative: serial monogamy." He concluded, "If the specter of legalized polygamy is the best argument against gay marriage, let the wedding bells ring." More recently, polygamy has gone to the heart of middle America with a TLC reality television show, Sister Wives, which features one man, four "wives" (he is legally married only to one of them), and sixteen combined kids.

Across the pond, in Britain in February 2008 a government panel recommended that as long as Muslim men married multiple women in countries where such unions are legal, then all the spouses should be eligible for state aid. That same year it was revealed that in the Netherlands polygamous marriages contracted elsewhere are commonly registered and recognized by Dutch authorities.

Back home, a pending court case is offering a defense of polygamy, with lead counsel and noted legal scholar Jonathan Turley of George Washington University arguing this summer in the New York Times that the Lawrence vs. Texas Supreme Court decision in 2003 should protect the private choices of polygamists.

From the labs: Three-person reproduction

Another route to legalized group marriage could evolve via new court decisions and expert proposals that recognize group-parenting arrangements. Judges in the U.S. and Canada have already given legal parental status to a sperm donor father whose offspring had two legal mothers -- resulting in the first instances ever in which a child has three legal parents. In New Zealand and Australia, commissions have recommended allowing egg and sperm donors to "opt in" as children's third legal parents. Meanwhile, scientists in the U.K. have received state permission to create embryos that have the DNA of three persons. It will not be long before group marriage proponents ask: How can children with three legal parents be denied the same marriage rights and protections for their families that children with only two parents have?

All of which begs questions: How do children feel when they are raised by three or more persons called their parents, especially when those people disagree? If their three-plus parents break up, how many homes do we expect these children to travel between? And why would anyone watching news coverage of arrests at polygamist compounds in Texas or British Columbia -- seeing hundreds of pale women wearing identical ankle-length dresses and braided hair amid reports of widespread abuse of and pregnancy among girls -- think that polygamy is compatible with a society that values women's rights and children's safety?

Get ready for the debate. And in the meantime, wedding planners: start figuring out how many brides and grooms you can fit down that aisle.